Hellas Planitia is a

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

located within the huge, roughly circular impact basin Hellas located in the southern

hemisphere Hemisphere refers to: * A half of a sphere As half of the Earth * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemisphere ** Land and water hemispheres * A half of the (geocentric) celes ...

of the

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

. Hellas is the third- or fourth-largest known impact crater in the Solar System. The basin floor is about deep, deeper than the Moon's South Pole-Aitken basin, and extends about east to west.The part below zero datum, see Geography of Mars#Zero elevation It is centered at Hellas Planitia spans the boundary between the Hellas quadrangle and the Noachis quadrangle.

Description

With a

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid f ...

of about , it is the largest unambiguous impact structure on the planet; the obscured

Utopia Planitia Utopia Planitia (Greek and Latin: "Nowhere Land Plain") is a large plain within Utopia, the largest recognized impact basin on Mars and in the Solar System with an estimated diameter of . It is the Martian region where the ''Viking 2'' lander to ...

is slightly larger (the

Borealis Basin The North Polar Basin, more commonly known as the Borealis Basin, is a large basin in the northern hemisphere of Mars that covers 40% of the planet. Some scientists have postulated that the basin formed during the impact of a single, large body ...

, if it proves to be an impact crater, is considerably larger). Hellas Planitia is thought to have been formed during the

Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypot ...

period of the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

, approximately 4.1 to 3.8 billion years ago, when a protoplanet or large asteroid hit the surface. The altitude difference between the rim and the bottom is over . The crater's depth of below the topographic

datum In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. ...

of Mars explains the atmospheric pressure at the bottom: 12.4 mbar (1240 Pa or 0.18 psi) during winter, when the air is coldest and reaches its highest density. This is 103% higher than the pressure at the topographical datum (610 Pa, or 6.1 mbar, or 0.09 psi) and above the

triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at which the ...

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

, suggesting that the

liquid phase A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, ...

could be present under certain conditions of temperature, pressure, and dissolved salt content. It has been theorized that a combination of glacial action and explosive boiling may be responsible for gully features in the crater. Some of the low elevation outflow channels extend into Hellas from the volcanic Hadriacus Mons complex to the northeast, two of which Mars Orbiter Camera images show contain gullies: Dao Vallis and

Reull Vallis Reull Vallis is a valley on Mars that appears to have been carved by water. It runs westward into Hellas Planitia. It is named after the Gaelic word for planet. It is found in the Hellas quadrangle. Lineated Floor Deposits On the floors of s ...

. These gullies are also low enough for liquid water to be transient around Martian noon, if the temperature were to rise above 0 Celsius. – page 2, para 3: Martian Gullies Mars#References Hellas Planitia is antipodal to

Alba Patera Alba Mons (formerly and still occasionally known as Alba Patera, a term that has since been restricted to the volcano's summit caldera; also initially known as the Arcadia ring) is a volcano located in the northern Tharsis region of the planet Ma ...

. It and the somewhat smaller

Isidis Planitia Isidis Planitia is a plain located within a giant impact basin on Mars, located partly in the Syrtis Major quadrangle and partly in the Amenthes quadrangle. At approximately in diameter, it is the third-largest obvious impact structure on the ...

together are roughly antipodal to the

Tharsis Bulge Tharsis () is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and A ...

, with its enormous shield volcanoes, while Argyre Planitia is roughly antipodal to

Elysium Elysium (, ), otherwise known as the Elysian Fields ( grc, Ἠλύσιον πεδίον, ''Ēlýsion pedíon'') or Elysian Plains, is a conception of the afterlife that developed over time and was maintained by some Greek religious and philos ...

, the other major uplifted region of shield volcanoes on Mars. Whether the shield volcanoes were caused by antipodal impacts like that which produced Hellas, or if it is mere coincidence, is unknown. Wikiterracimmeriaboundaries.jpg, MOLA map showing boundaries of Hellas Planitia and other regions Hellas basin topo.jpg, Geographic context of Hellas Image:False color of Hellas Planitia.jpeg, This elevation map shows the surrounding elevated ring of ejecta Image:Twisted Ground in Hellas.jpg, Apparent viscous flow features on the floor of Hellas, as seen by HiRISE. Image:Twisted Terrain in Hellas Planitia.jpg, Twisted terrain in Hellas Planitia (actually located in Noachis quadrangle). File:ESP 055080 1425twistedbands.jpg, Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program File:ESP 055212 1420taffypull.jpg, Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program These twisted bands are also called "taffy pull" terrain.

Discovery and naming

Due to its size and its light coloring, which contrasts with the rest of the planet, Hellas Planitia was one of the first Martian features discovered from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...

. Before

Giovanni Schiaparelli Giovanni Virginio Schiaparelli ( , also , ; 14 March 1835 – 4 July 1910) was an Italian astronomer and science historian. Biography He studied at the University of Turin, graduating in 1854, and later did research at Berlin Observatory, ...

gave it the name Hellas (which in Greek means ''

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...

''), it was known as ''Lockyer Land'', having been named by

Richard Anthony Proctor Richard Anthony Proctor (23 March 1837 – 12 September 1888) was an English astronomer. He is best remembered for having produced one of the earliest maps of Mars in 1867 from 27 drawings by the English observer William Rutter Dawes. His map w ...

in 1867 in honor of Sir Joseph Norman Lockyer, an English astronomer who, using a refractor, produced "the first really truthful representation of the planet" (in the estimation of

E. M. Antoniadi Eugène Michel Antoniadi (Greek: Ευγένιος Αντωνιάδης; 1 March 1870 – 10 February 1944) was a Greek-French astronomer. Biography Antoniadi was born in Istanbul (Constantinople) but spent most of his adult life in France ...

Possible glaciers

Radar images by the

Mars Reconnaissance Orbiter ''Mars Reconnaissance Orbiter'' (MRO) is a spacecraft designed to study the geology and climate of Mars, provide reconnaissance of future landing sites, and relay data from surface missions back to Earth. It was launched on August 12, 2005, an ...

(MRO) spacecraft's

SHARAD Sharad/Sarath/Sharath ( sa, शरद्)is the autumn season or ritu in the Hindu calendar. It roughly corresponds to the western months of mid-September to mid-November. Sharad is preceded by Varsha and followed by Hemant. The Hindu calendar c ...

radar sounder suggest that features called

lobate debris apron Lobate debris aprons (LDAs) are geological features on Mars, first seen by the Viking Orbiters, consisting of piles of rock debris below cliffs. These features have a convex topography and a gentle slope from cliffs or escarpments, which suggest fl ...

s in three craters in the eastern region of Hellas Planitia are actually glaciers of water ice lying buried beneath layers of dirt and rock. The buried ice in these craters as measured by SHARAD is about thick on the upper crater and about and on the middle and lower levels respectively. Scientists believe that snow and ice accumulated on higher topography, flowed downhill, and is now protected from sublimation by a layer of rock debris and dust. Furrows and ridges on the surface were caused by deforming ice. Also, the shapes of many features in Hellas Planitia and other parts of Mars are strongly suggestive of

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

s, as the surface looks as if movement has taken place.

Honeycomb terrain

These relatively flat-lying "cells" appear to have concentric layers or bands, similar to a honeycomb. This ''honeycomb terrain'' was first discovered in the northwestern part of Hellas. The geologic process responsible for creating these features remains unresolved. Some calculations indicate that this formation may have been caused by ice moving up through the ground in this region. The ice layer would have been between 100 m and 1 km thick. When one substance moves up through another denser substance, it is called a

diapir A diapir (; , ) is a type of igneous intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–T ...

. So, it seems that large masses of ice have pushed up layers of rock into domes that were subsequently eroded. After erosion removed the top of the layered domes, circular features remained. ESP 049330 1425honeycomb.jpg, Honeycomb terrain, as seen by HiRISE under

HiWish program HiWish is a program created by NASA so that anyone can suggest a place for the HiRISE camera on the Mars Reconnaissance Orbiter to photograph. It was started in January 2010. In the first few months of the program 3000 people signed up to use HiRIS ...

ESP 049330 1425honeycombcolor.jpg, Close, color view of honeycomb terrain, as seen by HiRISE under HiWish program 49330 1425honeycombcubes.jpg, Close view of honeycomb terrain, as seen by HiRISE under HiWish program 49330 1425honeycombcubesclose.jpg, Close view of honeycomb terrain, as seen by HiRISE under HiWish program This enlargement shows material breaking up into blocks. Arrow indicates a cube-shaped block. File:ESP 055080 1425twistedbands.jpg, Twisted bands on the floor of Hellas Planitia, as seen by HiRISE under HiWish program File:ESP 055001 1425honeycomb.jpg, Floor features in Hellas Planitia, as seen by HiRISE under HiWish program File:ESP 055067 1420ridgenetwork.jpg, Floor features in Hellas Planitia, as seen by HiRISE under HiWish program

Layers

Esp 037147 1430layers.jpg, Layers in depression in crater, as seen by HiRISE under HiWish program A special type of sand ripple called

Transverse aeolian ridges Transverse aeolian ridges (TARs) are visually bright features commonly found in topographic depressions on Mars. These small-scale and relict bedforms were first seen in narrow-angle images from the Mars Orbiter Camera (MOC) and were called “ridg ...

, TAR's are visible and labeled. ESP 045507 1470layers.jpg, Wide view of layers, as seen by HiRISE under HiWish program ESP 045507 1470layeredcrater.jpg, Close view of layered deposit in crater, as seen by HiRISE under HiWish program 45507 1470layerswhite.jpg, Layered formation, as seen by HiRISE under HiWish program 45507 1470layerswhiteclose.jpg, Close view of layers from previous image, as seen by HiRISE under HiWish program

Interactive Mars map

In popular culture

* Hellas Basin was a primary location in the 2017 video game ''

Destiny 2 ''Destiny 2'' is a free-to-play online-only multiplayer first-person shooter video game developed by Bungie. It was originally released as a pay to play game in 2017 for PlayStation 4, Xbox One, and Windows. It became free-to-play, utilizing th ...

''. The location is part of the second game's ''Warmind'' downloadable content. * It is also featured as a main location in the 2016 Bethesda video game reboot ''

Doom Doom is another name for damnation. Doom may also refer to: People * Doom (professional wrestling), the tag team of Ron Simmons and Butch Reed * Daniel Doom (born 1934), Belgian cyclist * Debbie Doom (born 1963), American softball pitcher * ...

''. *In ''Planet-Size X-Men #1'', the

X-Men The X-Men are a superhero team appearing in American comic books published by Marvel Comics, first appearing in Uncanny X-Men, ''The X-Men'' #1 by artist/co-plotter Jack Kirby and writer/editor Stan Lee in 1963. Although initially cancelled in ...

terraform Mars, turning the basin into Lake Hellas and building the Lake Hellas Diplomatic Ring, where galactic ambassadors can meet within the Sol system.

Notes

References

External links

* * – centered on Hellas * * {{Authority control Hellas quadrangle # Noachis quadrangle Plains on Mars